This application is a proposal to serve as the Statistical and Data Management Center of the Pediatric AIDS Clinical Trials Group (PACTG), in affiliation with the PACTG Coordinating and Operations Research Center application submitted by Dr. Stephen Spector. Our overall objectives and aims are to be responsible for all statistical and data management activities of the PACTG, including: (1) providing statistical and epidemiological support and leadership in the design and analysis of PACTG studies; (2) establishing and administering a central clinical and laboratory data management system; (3) collaborating with PACTG investigators on scientific and procedural issues and long-range planning, (4) proposing and conducting analyses of the PACTG database both within and across studies and in collaboration with other organizations, and (5) conducting statistical research on issues central to the PACTG's mission. The SDMC is accountable to the PACTG Group Chair and the Pediatric Executive Committee. To ensure that our responsibilities are completed in a timely manner and yield products of high quality, we have (1) established statistical and data management centers, each governed by a well-defined management, administrative and organizational structure that parallels and facilitates interactions with the PACTG protocol teams and committees; and (2) assembled a staff of highly-qualified and experienced specialists in the design, conduct and analysis of clinical trials and observational studies.